1. Field of the Invention
The present invention relates to a display device including a display panel having light emitting elements therein, and a method of driving the display device. In addition, the invention relates to an electronic device having the display device.
2. Description of Related Art
Recently, a display device using a current-drive optical element as a light emitting element in a pixel, the optical element being changed in emission luminance in accordance with a value of electric current flowing into the optical element, for example, an organic EL (Electro Luminance) element, has been developed and commercialized in a field of display devices for image display. The organic EL element is a self-luminous element unlike a liquid crystal element or the like. Therefore, a display device using the organic EL element (organic EL display device) does not need a light source (backlight) and therefore may be made small in thickness and high in luminance compared with a liquid crystal display device that needs a light source. In particular, use of active matrix as a drive method enables hold-lighting of each pixel, leading to low power consumption. Therefore, the organic EL display device is expected to become a mainstream of next-generation flat panel display.
The organic EL element, which is a current-drive light emitting element, may be adjusted in gray level by controlling the amount of current flowing into the organic EL element. However, in the organic EL element, an I-V characteristic varies depending on current application time or temperature of the element. Therefore, a drive transistor, which controls the amount of current flowing into the organic EL element, is constantly driven in a saturated region so that even if the I-V characteristic is temporally changed, constant luminance may be obtained (see Japanese Unexamined Patent Application Publication No. 2001-60076).